external/bsd/elftoolchain/dist/libelf/libelf_checksum.c

   1 /*      $NetBSD: libelf_checksum.c,v 1.2 2014/03/09 16:58:04 christos Exp $     */
   2
   3 /*-
   4  * Copyright (c) 2006,2008 Joseph Koshy
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 #include <sys/cdefs.h>
  30
  31 #include <gelf.h>
  32
  33 #include "_libelf.h"
  34
  35 __RCSID("$NetBSD: libelf_checksum.c,v 1.2 2014/03/09 16:58:04 christos Exp $");
  36 ELFTC_VCSID("Id: libelf_checksum.c 2225 2011-11-26 18:55:54Z jkoshy ");
  37
  38 static unsigned long
  39 _libelf_sum(unsigned long c, const unsigned char *s, size_t size)
  40 {
  41         if (s == NULL || size == 0)
  42                 return (c);
  43
  44         while (size--)
  45                 c += *s++;
  46
  47         return (c);
  48 }
  49
  50 unsigned long
  51 _libelf_checksum(Elf *e, int elfclass)
  52 {
  53         size_t shn;
  54         Elf_Scn *scn;
  55         Elf_Data *d;
  56         unsigned long checksum;
  57         GElf_Ehdr eh;
  58         GElf_Shdr shdr;
  59
  60         if (e == NULL) {
  61                 LIBELF_SET_ERROR(ARGUMENT, 0);
  62                 return (0L);
  63         }
  64
  65         if (e->e_class != elfclass) {
  66                 LIBELF_SET_ERROR(CLASS, 0);
  67                 return (0L);
  68         }
  69
  70         if (gelf_getehdr(e, &eh) == NULL)
  71                 return (0);
  72
  73         /*
  74          * Iterate over all sections in the ELF file, computing the
  75          * checksum along the way.
  76          *
  77          * The first section is always SHN_UNDEF and can be skipped.
  78          * Non-allocatable sections are skipped, as are sections that
  79          * could be affected by utilities such as strip(1).
  80          */
  81
  82         checksum = 0;
  83         for (shn = 1; shn < e->e_u.e_elf.e_nscn; shn++) {
  84                 if ((scn = elf_getscn(e, shn)) == NULL)
  85                         return (0);
  86                 if (gelf_getshdr(scn, &shdr) == NULL)
  87                         return (0);
  88                 if ((shdr.sh_flags & SHF_ALLOC) == 0 ||
  89                     shdr.sh_type == SHT_DYNAMIC ||
  90                     shdr.sh_type == SHT_DYNSYM)
  91                         continue;
  92
  93                 d = NULL;
  94                 while ((d = elf_rawdata(scn, d)) != NULL)
  95                         checksum = _libelf_sum(checksum,
  96                             (unsigned char *) d->d_buf, d->d_size);
  97         }
  98
  99         /*
 100          * Return a 16-bit checksum compatible with Solaris.
 101          */
 102         return (((checksum >> 16) & 0xFFFFUL) + (checksum & 0xFFFFUL));
 103 }